Do hardwood floors always buckle if there is a leak underneath?

Q: I have dark stains on my hardwood floor that I am noticing 3 years after a remodel. I suspect a leak, but the floor isn’t buckling. Do hardwood floors always buckle if there is a leak underneath?

A: A buckled floor would require a flood.

However, excess moisture often does cause some cupping with the board edges raising higher than the center when the water imbalance is from beneath.

Hardwood has lifted along some of the joints

Q imported from our old site, Face Lift Floors: Can you tell me how to fix hardwood flooring that has lifted along some of the joints (raised up) due to extreme cold( poor insulation under the overhang of the floor). It was put down in the summer and this winter it buckled along some of the seams, I think it was due to the cold winter (-35C) that we had.

A: I think what you are describing is called cupping. The edges of the boards are raised higher than the center of the board. There really is only one thing which causes this to occur. Excessively high humidity or moisture seeping under the floor, possibly from a leak in the roof, with water running down and inside the wall, for example. Moisture, rather than cold, per se is the culprit.

This situation is what one might have with extremely humid summers, and no climate control in ones home. Typically, in winter, with the heating system on, you need to add moisture to the air via humidifier or you may end up with gapping as the boards dry out and shrink. This happened on my own floors over this past winter, which was a long one. I got the humidifier going on the furnace and the problem corrected itself.

So, barring the absence of moisture by a leak, your cupping is difficult to explain. If this hardwood is installed in a second-floor bedroom with an open veranda beneath the front part of the room, you may have to find a way to insulate that space. Your problem is definitely moisture related. The boards expand and put pressure on the ones next to it, causing this “cupping”. Get the cause under control and the floor may correct itself over a few months.

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